Calcium-acidic phospholipid-phosphate (Ca-PL-P04) complexes have been shown to be associated with biological hydroxyapatite deposition. We will investigate the role of these complexes in (a) newly mineralizing tissues (healing rachitic rat cartilage and bone, (b) tissues with abnormal patterns of mineralization (osteopetrotic bone, osteoarthritic cartilage, salivary stones, dental calculus and other ectopic calcifications), and (c) tissues with altered lipid metabolism. For each of these studies, we will correlate the distribution and composition of isolated Ca-PL-P04 complexes with several, or all, of the following parameters; histological description, nature of mineral phases present, ash weight, hydroxyproline content, hexosamine content, total lipid content and composition, and DNA content. Concomitant in vitro studies will be made to delineate the mechanism of lipid-induced calcification. The structure of the Ca-PL-P04 complexes will be examined using transmission Electron Microscopy, 31P-Nuclear Magnetic Resonance, laser Raman Spectroscopy, infrared spectroscopy and x-ray small-angle scattering. A study will be made of the effect of the enzyme phospholipase A2 and alkaline phosphatase on lipid-induced calcification, both in vitro and in vivo. Finally, our present studies on the effect of proteoglycan subunits and aggregates on in vitro mineralization will be extended to include a study of the interaction of proteoglycans with lipid-induced hydroxyapatite proliferation.